This invention relates to multi-piece solid golf balls having improved flight performance, feel and durability.
For the purpose of improving the feel and other properties of two-piece solid golf balls, efforts have been made to develop multi-piece solid golf balls, typically three-piece solid golf balls. For example, Japanese Patent Nos. 2,614,791 and 2,880,688 disclose three-piece solid golf balls which are improved by controlling the hardness distribution of the solid core.
Japanese Patent No. 2,614,791 intends to improve the rebound and distance properties of the ball while maintaining appropriate spin, by maximizing the surface hardness of the core and gradually reducing the hardness of the core from its surface to its center. The present inventor found that the ball lacked anti-cracking durability when the surface hardness was maximum in the hardness distribution of the core. The ball cracked after a relatively small number of shots.
Japanese Patent No. 2,880,688 intends to improve the distance and controllability of the ball by minimizing the hardness distribution of the core. This patent discloses only those golf balls whose core has a substantially flat hardness distribution or a maximum hardness at its surface. The present inventor found that those golf balls whose core has a substantially flat hardness distribution or a maximum hardness at its surface and a reduced hardness difference between the surface and the center of the core have such spin properties that the flight performance on driver shots is less satisfactory (high spin receptivity on driver shots).
An object of the invention is to provide a multi-piece solid golf ball having improved flight performance, feel and anti-cracking durability.
The invention pertains to a multi-piece solid golf ball of three or more layer structure comprising a solid core, an intermediate layer, and a cover. The inventor has found that the ball is optimized in spin so as to acquire satisfactory flight performance when the hardness distribution of the solid core is adjusted such that the core does not have a maximum hardness at its surface, but has a peak or maximum hardness at a position spaced 3 to 10 mm radially inward from its surface, and the difference between the maximum hardness and the hardness at the core center is at least 3 JIS-C hardness units, and when the intermediate layer has a lower hardness than the cover. In addition, the ball offers a good feel when hit and is durably resistant to cracks so that the ball remains non-cracked after a large number of shots.
Therefore, the invention provides a multi-piece solid golf ball comprising a solid core, an intermediate layer around the core, and a cover around the intermediate layer, wherein the solid core has a maximum hardness at a position spaced 3 to 10 mm radially inward from its surface and a hardness at its center, the difference between the maximum hardness and the center hardness is at least 3 JIS-C hardness units, and the intermediate layer is softer than the cover.